THE GENECOLOGY OF LAWN WEEDS VI. THE ADAPTIVE SIGNIFICANCE OF VARIATION IN ACHILLEA MILLEFOLIUM L. AS INVESTIGATED BY TRANSPLANT EXPERIMENTS

Authors


SUMMARY

The performance of 21 populations of Achillea millefolium L., originating from I lawns, II grazed sites, III grasslands seasonally reduced in height by cutting and/or grazing and IV grassy areas not seasonally reduced in height by cutting and/or grazing, was investigated by transplanting clone-propagated material into a mature lawn. The response of a small number of contrasting populations was also studied in mown and tall grass plots of a reciprocal transplant experiment.

There was no evidence, from the mown treatment of either experiment, to support the hypothesis that A. millefolium populations originating from certain lawns or grazed sites, and notably dwarf in standard cultivation, were more successful than others in vegetative spread, dry wt yield or reproduction. In both experiments plants originating from lawns were not uniformly successful. Also, individuals from all four habitat groups proved to be vegetatively vigorous in mown plots. Six plants (three from lawns, two from pasture and one from waste ground) fruited successfully in the mown plots of the reciprocal transplant experiment.

Experiments with tall grass plots did not support the notion of tall grass races of A. millefolium. Such plots revealed considerable variability in all populations and plants from several habitat groups produced mature achenes in tall grass plots.

Fruiting of A. millefolium is very rare in well-kept lawns and the apparent clones in such habitats are likely to be the result of achene dispersal from habitats where the intensity and/or periodicity of grazing and/or mowing is insufficient to prevent fruiting.

Ancillary